#[test]
fn t_str1() {
    let mut s1 = String::new();
    let s2 = "s2".to_string();
    let s5 = &s2;
    let s3 = String::from("s3");
    //

    s1.push_str("s1");
    println!("{s1}, {s2}, {s3}");

    let s4 = s1 + &s2;
    println!("{s4}");

    println!("{s5}");
}

#[test]
fn t_str2() {
    let s1 = "hello你好".to_string();
    let s1chars = s1.chars();
    println!("{} {}", s1.len(), s1chars.count());

    let s2 = String::from("pp");

    let s3 = format!("{s1} {s2}");
    println!("{} ", s3);

    println!("=======================-");

    for i in s1.chars() {
        println!("{i}");
    }

    for ii in s1.bytes() {
        println!("{ii}");
    }
}
